Only read hydro properties when running with hydro

examples/main.c

@@ -360,7 +360,7 @@ int main(int argc, char *argv[]) {
 
   /* Initialise the hydro properties */
   struct hydro_props hydro_properties;
-  hydro_props_init(&hydro_properties, params);
+  if(with_hydro) hydro_props_init(&hydro_properties, params);
 
   /* Read particles and space information from (GADGET) ICs */
   char ICfileName[200] = "";